I was trying this, but I first couldn't get it to work (with the double wrapper for providing the arguments, but now found where the wrap should come. It's like this:
```
from functools import wrap
...
def deprecate_kwarg(old_arg_name, new_arg_name):
    def _deprecate_kwarg(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            ...
            return func(*args, **kwargs)
        return wrapper
    return _deprecate_kwarg
```